A Catalogue of the Insects, Mites and Pathogens that have been used or Rejected, or are Under Consideration, for the Biological Control of Invasive Alien Plants in South Africa

Abstract

This catalogue provides a comprehensive record of the 284 entities of organisms (insect, mite and pathogen species, or biotypes thereof) that have featured in biological control of invasive alien plants (weeds) in South Africa, since 1913. Fourteen of these entities are native species, or foreign species that have, by some unknown means, entered the country, while the remainder were intentionally imported specifically for biological control. The majority (237 of 284, i.e. 83 %) are phytophagous insects, the balance being made up of five species of mites (Acari) and 42 entities of plant-pathogens. The catalogue comprises the names of each of the target weeds, their origin, and an assessment of the degree of control that has been achieved with biological control, together with names and details (feeding guild, date released where applicable, current status and extent of damage inflicted) for each of the agents. Key references are provided. Of the 270 entities that were introduced into quarantine and tested for host specificity: 106 (39 %) were eventually released as biological control agents; 16 % are still under investigation; approximately 24 % were rejected by researchers because of doubts about their safety or efficacy; and 21 % have been shelved pending possible further study. Two of the pathogen species were developed as mycoherbicides. Seventy-five (71 %) of the 106 agents that were released in South Africa have become established on 48 invasive alien plant species, in 14 plant families. According to a rating system that has been widely adopted since 1999, and slightly amended in this account, approximately 21 % of the weed species on which biological control agents are established have been completely controlled, and another 38 % are under a substantial degree of control.